Apparatus for burning fuel at shear interface between coaxial streams of fuel and air



3,099,910 AR INTERFACE AIR 5 Sheets-Sheet 1 Aug. 6, 1963 R. M. scHlRMERAPPARATUS FOR BURNING FUEL AT SHE BETWEEN coAxIAL STREAMS oE EUEL ANDOriginal Filed Aug. 1l, 1955 INVENTOR. R. M.SCHIRMER ATTORN YS Aug. 6,1963 R. M. scHxRMl-:R 3,099,910

APPARATUS FOR BURNING FUEL AT SHEAR INTERFACE BETWEEN COAXIAL STREAMS 0FFUEL AND AIR Original Filed Aug. l1, 1955 5 Sheets-Sheet 2 mmm o mo omm, AM am. e o w e H//////// m eoe/ 3Q# 4 O www W///, R T T m /O/ M/M/fm mm mm mm wm w mw mm um uw. mm wn o HEAT INPUT RATE* BTU PER LB. AIR

INVENTOR. R M SCHlRMER ATTORNEY Aug. 6, 1963 R. M. SCH|RMER 3,099,910

APPARATUS FOR BURNING FUEL AT SHEAR INTERFACE BETWEEN COAXIAL STREAMS 0FFUEL AND AIR Original Filed Aug. l1, 1955 5 Sheets-Sheet 5 k\ Q na 4, o|600 f/ O l |500 |400 s? D u. 0 |300 ,L f FUEL |NJECT|0N Po|NT |200 E ATPER|P||ERY 0F om BURNER L ||o0 la, |000 E oq, 90o o '5 F soo D E 700 o U600 if 40o 200 |00 o o |00 200 30o 400 500 600 100 soo HEAT INPUTRATE-BTU PER LB. AIR

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NVENTOR.

ATTORNEYS 3,099,910 AR INTERFACE AIR 5 Sheets-Sheet 4 4 lTOR/ws rs Aug.6, 1963 R. M. scHlRMl-:R

APPARATUS FoR BURNING FUEL AT SHE BETWEEN coAxIAL STREAMS oF FUEL ANDOriginal Filed Aug. 1l, 1955 .EPI 5....",

R. M. scHlRMER 3,099,910 APPARATUS FoR BURNING FUEL AT sHEAR INTERFACEAug. 6, 1963 BETWEEN COAXIAL STREAMS OF FUEL AND AIR Original Filed Aug.1l, 1955 5 Shee'tsSheet 5 AT TORNEKS .Sk R

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.EE Si EAA.- i A United States Patent O Robert M. Schirmer,Bartlesville, Ghia? assiguor to Philli s Petroleum Company a corporationof Delaware Origpinal application Aug.11, 1955, Ser. No. 527,839.Divided and this application Apr. 26, 1962, Ser. No.

iso 34s 1i einen. (el. sii- 3954) This invention relates to improvedcombustors. In one of its more specific aspects, this inventionrelatesto combustion apparatus. In another of its more speciiic aspects,it relates to continuous flow combustion apparatus of low pressure drop,high combustion efliciency and high heat release. In another of its morespecmc aspects, this invention relates to an improved method forproducing continuous flow combustion at a 4high rate ofheat release. Inanother :of its more speciiic aspects, this 1nvention relates to a-combustor for jet engines. D

This application is ya division of my copending application Serial No.527,839, liled August l1, 1955, which in turn is a continuation-in-partof my copending .application Serial No. 346,304, filed April 2, 1953,now abandoned.

In the usual design of combustor apparatus in which a llame is initiatedin a stream of high velocity air, some mechanism must be provided toldecelerate at least a portion of the stream of air below effectivellame velocity in the combustible mixture to pilot and maintain thellame seated in the apparatus. Addition of fuel is made either directlyto the high velocity stream of air upstream of .the deceleration device:or in the region of a quiescent zone downstream of the decelerationdevice. In the usual turbo-jet engine, combustion is maintained in theflame tube or liner which completely surrounds the flames and aperturesin the liner serve for the addition of sufficient air for the formationof a near stoichiometric mixture of fuel `and air in its primarycombustion zone. The loss of pressure in an apparatus of this type isconsiderable. In the usual ram jet engine, a restrictive element,usually called la ame holder, is mounted in a .stream of high velocityair and combustion is piloted in the quiescent zone downstream fromrestriction. In this ram jet apparatus, the magnitude of the pressuredrop is usually less than that encountered in the turbojet engine.

In the lcombustion apparatus commonly employed in gas turbine powerplants, it is necessary to achieve stable and eflicient combustion offuel and air at high rates of heat release in a relatively coniinedspace through which a stream of air is moved at high velocity. It isdesirable in such a combustion system that the pressure loss be low,that the temperature distribution over the crosssection of ow be uniformand that stable and eicient combustion be obtained over 'a wide range offuel-air ratios and vseverity of inlet conditions.

The following objects will be obtained by at least one of the aspects ofthis invention.

A11 object of this invention is to provide an improved combustor.Another object of this invention is to provide an improved method forproducing continuous flow combustion at a high rate of heat release.Another object of the invention is .to provide `an apparatus of lowpressure drop in which improved combustion efficiency and stability areobtained. Another object of the invention is to provide an improved`combustor which does not require the conventional ame holder. Other andfurther objects of this invention -will be apparent to those skilled inthe art upon study of the accompanying disclosure and drawings.

3,099,910 Patented Aug. 6, 1963 ice I have now developed a combustion-apparatus which provides improved combustion eiciency and stabilitycompared to conventional apparatus with comparable pressure drops.Broadly speaking, my combustor permits the introduction of fuel,preferably vapor, along the wall of the flame tube, and .theintroduction of the air tangentially into an inner pipe so that the dowof air spirals or swirls `down the .axis of the burner. Stated anotherway, my invention provides for maintaining a separate strata of :fuel asan sannulus through which a swirling mass or vortex `of air is passed.When 4operating a combustor according to the method of my inventionseparate strata of fuel and air `are maintained within the primarycombustion zone or flame tube so that burning takes place at the shearinterface Ibetween the fuel and the air. In contrast to this type ofstructure and operation, in prior known burners there resultssubstantially complete rnixing of the fuel and air and combustion takesplace as a ball or column of flame moving `down the central portion oflthe combustion chamber. Heat release, in the order of 2() to 40 millionB.t.u./hour/cubic foot/atmosphere and higher have been obtained atoverall ow velocities up to 250 feet per second in the operation of mycombustor. This burner has particular application in operations wherehigh heat release is required, such as in gas turbines, turbo-jets, ramjets, furnaces, and the like.

The operation of a jet engine, such as those employed in aircraft, isdependent upon the utilization of the thermal energy released in theengine burner. The combustion of fuel and -air in the burner gives themolecules of the gases high kinetic energy. These gases are ejected fromthe combustion chamber at a high velocity, resulting from .the highkinetic energy provided by the thermal energy, and thrust is therebyapplied to the aircraft. Thus the performance of -a jet engine can belimited by its ability to obtain high heat release under all operatingconditions. The improved burner of my invention has particularapplication in operations where high heat release is required, such asin gas turbines, ram jets, furnaces, and the like.

In my combustion apparatus, all of the air may be used as primary air,or part of the air may be used for secondary air, depending upon theneed and adaptation of the burner. Primary air is admitted through aplurality of tangential openings into the llame tube. Preferably, theseopenings are tangential to the flame tube or to an inner short length ofpipe Iand allow the injected primary air to make a tangential jet intothe larger flame tube; said openings are located around the periphery ofthe flazne tube or around the periphery of said inner short length ofpipe located immediately upstream from the flame tube. In anotherpreferred embodiment the air can be admitted coaxially to the flame tubethrough swirl vanes so as to produce a swirling mass of air spiralingcoaxially and helically through the ame tube. These methods provide `aswirling Iand spir-alling ilow :of air down the axis of the burner andprovide for the supply of the right amount of air to the fuel over aconsiderable operating range so as to rigidly control fuel residencetime, limiting pyrolytic carbon formation as is normally desired for jetengine operation.

The fuel, prefenably Vaporized, is injected into an annular space at theinner surface of the flame tube and flows down the inner wall of thellame tube. Any fuel which may be prevaporized is particularly suitablefor use in this burner. A liquid or even a solid fuel may be used in theproper modification of the apparatus. When using a, liquid fuel, it maybe desirable to use a plurality of -atomizing Inozzles to form a linemist for spraying in the annular space and to provide iiow of the fueldown the wall of the flame tube. A solid fuel should preferably exist in-a very finely divided state.

The method of introduction of air and fuel in my Iburner provides atangential core of air which `swirls through an annulus of fuel,preferably prevaporized, with mixing being accomplished at the extensiveshear interface between the fuel and air streams. In my burner the wallof the ame tube is blanketed with said annulus of fuel. Thus, fulladvantage is taken of the radiant energy of the flames to preheat, andperhaps pyrolyze, the fuel. It maybe that such fuel preheating andpyrolysis produces materials having a high dame-speed, i.e., materialssuch as hydrogen, acetylene, ethylene, etc., which stabilize combustion.Combustion apparently is effected at the highly turbulent shearinterface between the fuel and the air, and therefore the combustionoccurs near the periphery of the flame tube `and in the mixing zone atsaid interface. The characteristics of controlled fuel residence timeand organized air turbulence with intense mixing at the shear interfacealong the flame tube provides a superior performance burner. Thisarrangement in the burner apparently provides for the supply of acombustible fuel-air mixture over .a Wide operating range as evidencedby the constant and high value of combustion eciency obtained. Theamount of heat release per unit volume of combustion chamber that can-be `obtained with my improved combustion method and apparatus is atleast ten fold that of conventional burners now commonly employed.

In vaddition to the higher heat release obtained, my burner is superiorto known burners in that it deposits less carboh in the flame tube andforms less smoke than do other burners. In fact, fuels now generallyconsidered unsatisfactory because of their carbon deposition tendencies,e.g. benzene etc., can be :burned satisfactorily in my burner. Asub-critical residence time for all the fuel introduced into this burnerprobably explains the lack of carbon deposition on the walls of theburner and lack of smoke in the exhaust. Probably insufficient time isallowed for the dehydrogenation and polymerization of the fuel to form-carbon particles.

In the drawings, FIGURE 1 is a sectional elevation of an improvedcombustor of my invention;

FIGURE 2 is a cross-section taken along the line 2-2 of FIGURE 1;

FIGURE 3 is a section view showing a modification of the combustor ofFIGURE 1;

FIGURE 4 is a cross-section taken along the line 4-4 of FIGURE 3;

FIGURE 5 is a graphic representation showing a comparison of resultswhen using axial and peripheral fuel input;

FIGURE 6 is a section view showing a preferred nonstep modification ofthe combustor of FIGURE l; and

FIGURE 7 is a graphic representation showing the results of Iburningnormal heptane and a burner such as the one shown in FIGURE 3.

FIGURE 8 is a sectional elevation vof another modification of theimproved combustor of this invention.

FIGURE 9 is a cross-section taken along the line 9-9 of FIGURE 8.

FIGURE l0 illustrates an application of the combustor of FIGURE 8 in aturbo-jet engine.

FIGURE l1 illustrates an application of a combustor of FIGURE 8 in aram-jet engine.

Referring particularly to the device shown as FIG- URE 1 of the drawing,combustor 11 comprises an outer shell 12 which may be integral with theenlarged upstream end thereof or may be connected to the upstream endportion 12 by means of flange members 13 and 14. Flame tube 15 iscoaxially disposed within lshell 12 and shell 12', extending froma pointwithin shell 12 to the downstream end of shell 12. Igniter tube 16 ispositioned within the upstream end portion of flame tube 15 and issupported therein by closure member 17. Igniter tube 16 is smaller incross-section than flame tube 15 and extends a `short distance into theupstream end of flame tube 15. An annular space 18 is formed between thedownstream end of igniter tube 16 and the upstream end of ame tube 15and is preferably formed so as to direct gaseous materials outwardlyagainst the wall of ame tube 15. Fuel inlet conduit means 19 extendsthrough closure member 17 to the -annular space 18, soas to providemeans for introducing fuel into the annular space surrounding theigniter tube.

Igniter 21 extends through closure member 17 into the interior ofigniter tube 16. An annular space 22 is preferably formed betweenigniter 21 and the downstream end of closure member 17. Pilot fuel inletconduit 23 extends through closure member 17 into annular space 22 so asto provide means for introducing pilot fuel into that annular space. Airinlet conduit 24 opens into the annular space formed between shell 12and flame tube 15. A plurality of primary air inlet conduits 25 extendstangentially from the annular space formed between shell 12 and ignitertube 16 through igniter tube 16 and open into the interior thereof. Aplurality of secondary air inlet conduits 26 extends through llame tube15 at a point downstream of the primary combustion zone. Secondary airinlet conduits 26 communicate with the continuous air passage formedbetween shell 12' and shell 12 and ame tube 15. If desired, wells areprovided for the introduction of 4thermocouples at points 27 so thatconstant observation of temperatures can be obtained.

In the operation of the device shown in FIGURE 1 of the drawings, fuelsuch as the primary fuel or propane is introduced as pilot fuel throughconduit 23 into the annular space formed between closure member 17 andigniter 21. Primary air is introduced through conduit 24 and theplurality of tangential primary yair inletconduits 25 into the ignitertube 16 at a point adjacent the downstream end of annular conduit 22.'Ihe pilot fuel is ignited in igniter tube 16. The air which isintroduced through tangential inlet conduit 25 imparts a helical motionto the gases owing through igniter tube 16 and into the interior offlame tube 15. Primary fuel is introduced into the annular space 18 fromfuel inlet conduit 19. Vaporization may take place in annular space 18in an indirect heat exchange with the regular flame or the pilot llame.One or more primary fuel inlet conduits can be utilized if desired. Ifdesired the -fuel can be prevaporized. The primary fuel is directedslightly outwardly onto the inner wall of ame tube 15 and flows downsaid wall past the point of introduction of the incoming primary airmoving in a helical direction, thus obtaining controlled mixing at theshear interface between said fuel and air. The primary fuel and airmixture is ignited by the burning pilot fuel, lafter which time theintroduction of pilot fuel may be discontinued. By introducing the fuelslightly outwardly against the wall of iiame tube 15 and introducing theprimary air in a helical motion, controlled mixing of the fuel and airisobtained without the aid of holding means such as a arne holder whichwould increase the pressure drop through the unit. The combustionefliciency obtained in this type of device is therefore very good.

A portion of the primary air which is introduced through conduit 24 isdiverted as secondary air and is introduced into the interior of ametube 15 downstream of the primary combustion zone. This secondary airacts as a quench, `diluting the combustion products to such an extentthat additional burning does not occur. The addition of secondaryair'also tends to even olf the temperature of rgas phases in thecombustor.

The secondary air is not required when the hot combustion gases do notflow to a turbine or other apparatus harmed by high temperatures.

Referring particularly to the device found in FIGURE 3 of the drawings,parts which 'are like those described in connection with FIGURE l of thedrawings `are indicated by like numerals. In this particularmodification, primary air is introduced itangentially into a chamber ofabout the same cross-section as that of flame tube 15. Primary air inletconduits 25 extend from the annular chamber formed between shell 12 and-ame tube 1S into the interior of an igniter zone which is of innerdiameter but slightly smaller than the inner diameter of ame tube 15.Annular space 18 is provided so as to inject primary fuel directly alongthe wall Iof flame tube `15. Primary fuel inlet conduit 19 is connectedto annular space v18. Introduction of fuel and in this manner has thesame advantageous results as obtained in the one described in connectionwith FIGURE 1 `of the drawing.

When the total fuel is introduced into the combustion chamber axially,as through the pilot fuel inlet conduit, the resulting combustionefficiency is very low at lean fuel-air mixtures. In diverting theintroduction of the primary fuel out to the wall of name tube 15, l havematerially increased the combustion efficiency of the burner. Myarrangements which allow the air to swirl out of the igniter tube andalong the flame tube so as to mix with the fuel, provide for a supply ofthe right amount of air to fuel lover ya considerable operating range asillustrated by the constant and high value of combustion efficiencyobtained as shown in FGURE of the drawings.

A small scale burner having a flame .tube inner diameter of about 2inches and a combustor length of about 1 foot was utilized in :obtainingthe data set forth in FIGURE 5 of the drawings. An air inlet velocity of187 feet per second, mass air flow rate of 0.30 lb./sec., inlet staticpressure of 40 inches of mercury absolute, an inlet air temperature of300 F., and inlet temperature of 400 F., and a normal heptane fuel wereutilized as conditions of operation in yobtaining the data `set forth inFIGURE 5. As will be noted, considerably better combustion efficiencywas obtained at lean fuel-air ratios when using the annular fuelinjection at the wall of a combustor using tangential air inlets, thanwas obtained when using an axial fuel inlet in such a combustor.

A small scale burner having a flame tube inner diameter of about 2inches and a combustor length of about l foot, but utilizingsubstantially no step, i.e., the interval from the outside of theignited tube to the inside of the flame tube, was utilized in obtainingthe data set forth in FIG- URE 7 of the drawings. An air inlet velocityof 171 feet per second, mass air flow rate of 0.30 lb./ second, inletstatic pressure of 50 inches of mercury absolute, an inlet airtemperature of 200 F., an inlet fuel temperature of 400 F., `and normalheptane fuel were utilized as conditions of operation in obtaining thedata set forth in FIG- URE 7. These data also indicate the excellentcombustion efciency which is to be lobtained with the improved combustorof this invention.

Although this invention has been particularly described in connectionwith a combustor utilizing an igniter tube, the use of such a tube isnot required. In fact, I have discovered that combustion eciency ismaterially improved when the step Ifrom the igniter tube to the llametube is decreased in size. The larger 'size step results in a back ilowwithin the combustor, which is detrimental to combustion ethciency. Oneof the problems erdsting in the operation of conventional jet engines isthat combustion :eliiciency is materially reduced with most conventionalengines When utilizing fuels other than a normalparalin, i.e., aromaticsand the like. I have found that when a device, such as -is shown inFlGURE 3 of the drawings, is utilized, the combustion efficiency ofaromatics is materially improved over that obtained in the operation ofthe device set forth in FIGURE 1, despite the fact that the device shownin FIGURE 1 gives a much better combustion eiciency than is obtainedwith conventional combustors.

In the device shown as FIGURE 6 of the drawings, the igniter tube hasbeen omitted and fuel is injected from the annular space 18 intorecesses 2S' formed in the wall of ame tube 15, sloping inwardly and ina downstream direction. By introducing the fuel in this manner, thedownstream tlow of fuel is firmly established before it is contactedwith the helical flow 0f air introduced through conduits 25. It ispreferred that the point of fuel introduction be at least as fardownstream as the point of introduction of the primary air. However,when utilizing the device of FIGURE 6 of the drawings, wherein therecesses 28 are formed in the wall of the ilame tube, the fuel can beintroduced into the recesses at a point upstream iof the inlets 25 solong as the fuel does not emerge from the recesses until it has passedto points downstream of inlets 25. Recesses 28 are preferably formedbetween the openings fof conduits 25.

Referring particularly to the device lshown in FIGURE 8 of the drawings,pants which are like those described in FIGURES 1 and 3 of the drawingsare indicated by like reference numerals. In this particularmodification, the combustion apparatus comprises an `outer shell 12having a flame tube 15 coaxially disposed within shell 12. The upstreamend of llame tube 15 is positioned within annular support member 31which is suitably supported Within said outer shell 12 by suitable meanssuch as rods, not shown. Annular support member 31 forms an annulusbetween said outer shell and said llame tube. Second support member 29is coaxially positioned annular support member 3l1 so as to form asecond annulus between said annular support member and said coaxiallypositioned member 29. Air inlet 20 is connected to said outer shell 12by means of flange members 13 and 14. Fuel inlet conduit 19 extendsthrough air inlet 20' and support member 31 to annular space 1S in saidsupport member 31. Pilot fuel conduit 23, which extends through airinlet means 20 and annular support member 31, supplies fuel for ignitionpurposes to annular space 22 recessed into the downstream side of member29. Igniter 21 extends through member 29 into said chamber 22 foreffecting ignition of a pilot fuel such as propane. Igniter 21 can -beof a spark type Ior other suitable device. Swirl vanes 30, positioned insaid second annulus, impar-t a swirling helical motion to air admittedto llame tube 15 so as to form a swirling mass of air within said flametube. Said swirl vanes can be of different types such as, for example,air foil sections, la helix along the inner periphery 'of support member31, etc. A plurality of secondary \air inlet conduits 26 extend throughame tube 15 at a point downstream of the primary combustion zone.Secondary air inlet conduits 26 communicate with the continuous passageformed between shell air inlet 20", outer shell 12, and flame tube 115.

In the operation of the device shown in FIGURE 8, fuel such as theprimary fuel, or a pilot fuel such as propane is introduced as pilotfuel through conduit 23 into annular space 22. Primary air is introducedthrough air inlet 20 and swirl vanes 30 into the llame tube orcombustion chamber. The pilot fuel is then ignited in annular chamber 22by means of igniter device 21.

Primary fuel, which can be in gaseous or vaporous form, is introducedinto annular space 18 by means of fuel inlet conduit 19. Said primaryfuel is directed outwardly against and along flame tube y15 so as toform an annulus of said fuel around the periphery of said flame tube.Swirl vanes 30 impart a swirling helical motion to the air introducedinto said flame tube, which air travels as a vortex or helicallyspiraling mass within said annulus of fuel. Said primary fuel and airform a mixture a-t the interface therebetween, which mixture is ignitedby the burning pilot fuel, after which the introduction of pilot fuelcan be discontinued. By thus Iintroducing the fuel uniformly along thewall of the combustion chamber or name tube so as to yform an annulus ofsaid fuel around the periphery of said ame tube, and introducing ltheprimary air as a helically swirling mass within said annulus of Vfuelwhich travels coaxially and longitudinally `of said ilame tube,excellent mixing of said fuel and air at the shear interface between thetwo streams is obtained and a stable flame results.

Although the combustion apparatus of this invention is e primarilyemployed in continuous combustion type gas turbine power plants,including stationary as well at jet engine power plants, said combustionapparatus is not limited to lsaid `applications but can also be employedin furnaces or similar oil-burning installations employed for otherpurposes. Since very little smoke is produced, due to the highlcombustion efficiencies obtained, said cornbustion apparatus isparticularly adapted for employment in congested urban areas where airpollution due to smoke, smog, etc., is a problem. The apparatus can alsobe employed for carrying out chemical reactions involving combustion.

Various other modifications of this invention will be apparent to thoseskilled in the art upon study of the accompanying disclosure. Suchmodifications are believed to be within the spirit and scope of thisinvention.

l cla-im:

l. An improved combustor comprising: an elongated llame tube open `atits downstream end; a plurality of recesses longitudinally disposed inthe upstream end portion of the inner Iwall of said flame tube andsloping inwardly toward the downstream end of said flame tube and towardthe surface of said inner wall; `annular fuel inlet means adjacent theupstream end of said llame tube, the downstream opening of said fuelinlet means being directed into said recesses for introducing fuel ontosaid inner wall and passing said fuel as an `annulus in a downstreamdirection along -said inner wall; yand air inlet means for introducingand passing a swirling vortex of air coaxially throu-gh said llame tubewithin said annulus of fuel to effect the formation of a shear interfacebetween said fuel and said air so that ysaid fuel burns wit-h an annularame at said shear interface.

2. A burner comprising: an elongated flame tube open at its downstreamend; -a plurality of recesses longitudinally disposed in and around theups-tream end portion of the inner wall of said ame tube and slopinginwardly toward the downstream end of said flame tube and toward thesurface of said inner wall; annular fuel inlet means adjacent theupstream end of said flame tube, the downstream opening of said fuelinlet means being directed into said recesses for injecting and passingan annulus of yfuel in a downstream direction in and along theperipheral portion of said flame tube; and air conduit means extendingtangen-tially into the upstream end portion of said llame tube forintroducing and passing a swirling stream of air helically along theinner surface of said annulus of fuel -to effect the formation of ashear interface between said air and :said -fuel so that said fuel burnswith an annular ame at said shear interface.

3. An improved combustor comprising: an outer shell closed at itsupstream end; an elongated llame tube spaced from said outer shellintermediate its ends, closed at its upstream end and open at itsdownstream end; air inlet means in lthe upstream end portion of saidouter shell; air inlet conduits extending tan-gentially from the chamberformed between said outer shell and said flame tube into the upstreamend portion of said flame tube; a plurality of recesses longitudinallydisposed in the upstream end portion of the inner wall of said ame -tubeand sloping inwardly toward the downstream end of said arne tube andtoward the surface of said inner wall; and fuel inlet means opening intosaid recesses for introducing fuel onto the inner wall of said flametube.

4. The improved combustor of claim 3 wherein said fuel inlet meanscomprises at least one fuel inlet conduit terminating in a fuel nozzle,an annulus opening to said inner wall of said flame tube, and fuelconduit means extending between said fuel nozzle and said annulus.

5. An improved combustor comprising: an outer `shell closed at itsupstream end; an elongated flame tube spaced Ifrom said outer shellintermediate its ends, closed yat its upstream end and open at itsdownstream end; air -inlet means in the upstream end portion of saidouter shell; air inlet conduits extending tangent-ially from the chamberformed between said outer she-ll and said llame `tube into the upstreamend por-tion of said flame tube; a plurality of 'recesses longitudinallydisposed in the upstream end portion of the inner wall of said flametube and sloping inwardly toward the downstream end of said ame tube andtoward the `surface of said inner wall; fuel inlet means opening intosaid recesses for introducing lfuel onto the inner wall of said flametube; -and secondary air conduits extending from the chamber formedbetween said outer shell and said iiame tube into the interior of saidflame tube at a point downstream of a primary combustion zone therein.

6. Animproyed combustor comprising an outer shell closed at its upstreamend; an elongated flame tube spaced from said outer shell intermediateits ends, closed at its upstream end and open at its downstream end; aplurality of recesses longitudinally disposed in the upstream endportion of the inner wall of said flame tube and sloping inwardly towardthe downstream :of said iiame tube and toward the inner surface of saidinner wall; annular fuel inlet means adjacent the upstream end of saidflame tube, the downstream opening of said fuel inlet means opening intosaid recesses in a downstream direction for injecting and passing anannulus of fuel in a downstream direction limited substantially tolongitudinal movement along said inner wall of said flame tube; yairinlet means in said -outer shell; and 'air conduit means extending fromthe chamber formed between said outer shell and said llame tube fortangentially introducing a swirling stream of air into the upstream endof said flame tube and passing same helically `along the inner surfaceof said annulus of fuel to effect 4the formation of a shear interfacebetween said air and said fuel so that said fuel burns with an -annularflame at said `shear interface.

7. The combustor of claim 6 wherein said recesses are positionedintermediate said air conduit means.

8. An improved combustor comprising: an outer shell closed at itsupstream end; an elongated flame tube spaced from said outer shellintermediate its ends, closed art its upstream end and open at itsdownstream end; a plurality of recesses longitudinally disposed in andaround the upstream end portion of the linner wall of said flame tubeand sloping inwardly toward the downstream end of said flame tube andtoward the surface of said inner wall; annular fuel inlet means adjacentthe upstream end of said ame tube, the downstream opening of said fuelinlet means being directed into said recesses for introducing fuel ontothe inner wall of said iiame tube and passing said fuel as an annulusalong said inner wall in a direction limited substantially toflongtuidinal movement; air inlet means in said outer shell; air conduitmeans extending from the chamber between said outer shell and said ilametube `for introducing air into the interior of said upstream end of saidflame tube through tangential openings positioned intermediate saidrecesses and passing said air as a swirling stream within and adjacentsaid annulus of fuel to eect the formation of a shear interface betweensaid air and said fuel so that said fuel burns with an annular ame atsaid shear interface.

9. An improved combustor comprising, in combination: a first outercylindrical shell portion open at each of its ends; a second outercylindrical shell portion larger in inner diameter through a portion oflits length than the inner diameter of said rst outer cylindrical shellpontion and replaceably connected to the upstream end of said firstcylindrical shell portion, the upstream end of said second outer shellportion being closed; an elongated cylindrical flame tube concentricallypositioned within and spaced from said outer shell portions, and closedat its upstream end; a plurality of recesses longtiudinally disposed inand around the upstream end portion of the inner wall of said flame tubeand sloping inwardly toward the downstream end of said flame tube andtoward the surface of said inner wall; annular fuel inlet conduit meansadjacent the upstream end of said flame tube, the downstream opening ofsaid fuel inlet means being directed into said recesses for introducingand passing an annulus of fuel in a downstream direction limitedsubstantially to longitudinal movement along said inner wall of saidflame tube; air inlet means opening into the enlarged portion of saidsecond outer shell; air conduit means extending tangeutially from thechamber formed between said enlarged second outer shell portion .andsaid llame tube into the upstream end portion of said flame tube forintroducing a swirling vortex of air into the interior of said llametube and passing said air through said annulus of fuel to effect theformation of a shear interface between said fuel and said air so thatsaid fuel burns with an annular flame at said shear interface; andsecondary air conduit means extending from the chamber formed betweensaid first outer shell and said ame tube into the interior of said flametube at a point downstream of a primary combustion zone in said ametube.

l0. -An improved combustor comprising: an outer shell open at itsupstream end; an elongated impervious flame tube open at its downstreamend, positioned concentrically within and spaced apart from said outershell; an annular closure and support member positioned at the upstreamend of said outer shell and the upstream end of said llame tube andforming an axially positioned annular space at said upstream end of saidflame tube; an igniter extending through said annular closure andsupport member into said annular space; a pilot fuel inlet conduit alsoextending through said annular closure and support member into saidannular space; a plurality of recesses longitudinally disposed in andaround the upstream end portion of the inner wall of said flame tube andsloping inwardly toward the downstream end of said flame tube and towardthe surface of said inner wall; fuel inlet conduit means extending meansinto said annular closure and support member and terminating in anannular chamber Within said annular closure and support member adjacentthe inner periphery of the upstream end of said llame tube, thedownstream opening of said annular chamber being directed tinto saidrecesses for introducing and passing an annulus of fuel in a downstreamdirection limited to substantially longitudinal movement along saidinner wall of said llame tube; air `inlet means opening into said outershell; air conduit means extend-ing tangentially from the charnberformed between said outer shell and said llame tube into the upstreamend pontion of said flame tube for introducing a swirling stream of airinto said upstream end of said ame tube axially of said tube and passingsame in a swirling helical pattern within and adjacent said annulus offuel to effect the formation of a shear interface between said air andsaid fuel so that said fuel burns with an annular flame at said shearinterface; and secondary air conduits extending from said chamberbetween said outer shell and said llame tube into the interior of satidflame rtube at a point downstream of a combustion Zone therein.

lll. An improved combustor comprising an outer shell closed at itsupstream end; an elongated flame tube spaced from said outer shellintermediate its ends, closed at its upstream end and open at itsdownstream end; air inlet means lin said outer shell; air conduit meansextending from the chamber formed between said outer shell and saidflame tube to tangentially introduce air into the upstream end of saidflame tube; recesses longitudinally disposed in the upstream end of saidflame tube and sloping inwardly toward the downstream end of said flametube and :to the inner surface thereof; and fuel inlet means in saidrecesses directed in a downstream direction.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION August 6, 1963Patent No. 3,099,910

Robert M. Schirmer It is hereby certified that error appears in theabove numbered patent reqiiring correction and that the said LettersRatent should read as corrected below.

for "lonq'tuidnal" read longitudinal t formed column 9, line line 14,after "shell" strike out "means".

Column 8, line 48, line 50, after "chamber" inser insert inlet column 9,line 34,

y of February l964.

'- l3, after "air insert portion Signed and sealed this 25th da Anm:ERNEST W; SWIDER EIJEJI' L. RFI'I'NOLDS Attesting Officer AC L i n@Commissioner of Patents

1. AN IMPROVED COMBUSTOR COMPRISING: AN ELONGATED FLAME TUBE OPEN AT ITSDOWNSTREAM END; A PLURALITY OF RECESSES LONGITUDINALLY DISPOSED IN THEUPSTREAM END PORTION OF THE INNER WALL OF SAID FLAME TUBE AND SLOPINGINWARDLY TOWARD THE DOWNSTREAM END OF SAID FLAME TUBE AND TOWARD THESURFACE OF SAID INNER WALL; ANNULAR FUEL INLET MEANS ADJACENT THEUPSTREAM END OF SAID FLAME TUBE, THE DOWNSTREAM OPENING OF SAID FUELINLET MEANS BEING DIRECTED INTO SAID RECESSES FOR INTRODUCING FUEL ONTOSAID INNER WALL AND PASSING SAID FUEL AS AN ANNULUS IN A DOWNSTREAMDIRECTION ALONG SAID INNER WALL; AND AIR INLET MEANS FOR INTRODUCING ANDPASSING A SWIRLING VORTEX OF AIR COAXIALLY THROUGH SAID FLAME TUBEWITHIN SAID ANNULUS OF FUEL TO EFFECT THE FORMATION OF A SHEAR INTERFACEBETWEEN SAID FUEL AND SAID AIR SO THAT SAID FUEL BURNS WITH AN ANNULARFLAME AT SAID SHEAR INTERFACE.